An inguinal hernia is formed when small a loop of bowel or intestine protrudes through a weak place or defect within the lower abdominal muscle wall or groin. This condition is rather common, particularly in males. Hernias of this type can be a congenital defect or can be caused by straining or lifting heavy objects. The protrusion results in an unsightly bulge in the groin area often causing pain, reduced lifting ability, and in some cases, impaction of the bowel.
Surgery is a common solution to this problem. The preferred surgical technique requires extracting the bowel from the defect, placing a surgical prosthesis such as a mesh patch over the open defect, and attaching the mesh patch to the inguinal floor with conventional sutures or with surgical fasteners or anchors. The repair is accomplished using either open or laparoscopic surgery. Surgical anchors are routinely used in the laparoscopic procedures owing to the difficulty in suturing under laparoscopic conditions.
At present, there are a variety of surgical devices and fasteners available for the surgeon to use in endoscopic or open procedures to attach the mesh patch to the inguinal floor. One such mesh attachment instrument uses a helical wire fastener formed in the shape of a helical compression spring. Multiple helical wire fasteners are stored serially within the 5 mm shaft, and are screwed or rotated into the mesh and the overlaid tissue to form the anchor for the prosthesis. A load spring is used to bias or feed the plurality of helical fasteners distally within the shaft. A protrusion extends into the shaft, while preventing the ejection of the stack of fasteners by the load spring, allows passage of the rotating fastener. U.S. Pat. Nos. 5,582,616 and 5,810,882 by Lee Bolduc, and U.S. Pat. No. 5,830,221 by Jeffrey Stein describe instruments and fasteners of this type.
U.S. Pat. Nos. 5,203,864 and 5,290,297 by Phillips describe two embodiments of a hernia fastener and delivery devices. One of the Phillips fasteners is formed in the shape of a unidirectional dart with flexible anchor members. The dart is forced through the mesh and into tissue by a drive rod urged distally by the surgeon's thumb. The anchor members are forced inward until the distal end of the dart penetrates the overlaid tissue and then the anchor members, presumably, expand outward forming an anchor arrangement. Multiple darts are stored in a rotating cylinder, much like a revolver handgun. Phillips second fastener embodiment is a flexible H shaped device. The tissue penetrating means is a hollow needle containing one of the legs of the H. The H shape is flattened with the cross member and the other leg remaining outside the hollow needle owing to a longitudinal slot therein. A drive rod urged distally by the surgeon's thumb again delivers the fastener. The contained leg of the H penetrates the mesh and tissue. After ejection the fastener presumably returns to the equilibrium H shape with one leg below the tissue and one leg in contact with the mesh with the cross member penetrating the mesh and the tissue, similar to some plastic clothing tag attachments.
A series of patents, U.S. Pat. Nos. 6,572,626, 6,551,333, 6,447,524, and 6,425,900 and patent applications 200200877170 and 20020068947 by Kuhns and Kodel, all assigned to Ethicon, describe a super elastic, or shape metal fastener and a delivery mechanism for them. The fasteners are stored in the delivery device in a smaller state and upon insertion into the mesh and tissue transitions to a larger anchor shaped state owing to warming above the super elastic transition temperature from body heat. The Ethicon fastener is delivered by an elaborate multistage mechanism through a hollow needle that has penetrated the mesh and the tissue. The hollow needle is then retracted to leave the fastener to change shape, owing to the temperature transition, to a more suitable configuration for holding the mesh in place.
There are several problems associated with the prior art. The method of penetration of the helical fastener is the same as a wood screw, for example, in that the rotational thread action provides mechanical advantage for the advancement of the fastener through the mesh and tissue. The helical fastener, however, does not have a head or stop on the proximal end so that it can often be screwed all the way through the mesh and into the tissue and thus providing no fastening support for the mesh. As with any screw a pointed distal end is required to cause the screw to start into the material. This configuration can cause permanent pain for some placements of the fastener and sometimes results in the need for the fastener to be excised from the body in a subsequent surgical procedure.
Both the Phillips dart and H shape fastener must be placed in soft enough tissue that will allow the anchor members to deploy or else the holding strength is severely compromised.
The Ethicon device is very complex and expensive to manufacture owing to the delivery mechanism and the cost of the super elastic fastener material. In addition the proximal end of the fastener is not symmetric so that care must be taken to orient it correctly so that both proximal leg members contact the mesh, since fasteners are almost always deployed near the edges of the mesh. Another problem with the Ethicon device is that the delivery tube is 5 mm in diameter and the surgeon must hold a counter force with the palm of the hand on the handle to hold the delivery tube against the mesh while simultaneously applying an oppositely directed force to the trigger (actuator) with his fingers of the same hand. The trigger is spring-loaded and requires a substantially larger force than the tissue penetrating force. These forces change throughout the actuator stroke as the spring loads increase. In addition, the penetrating force peaks then suddenly decreases as the initial penetration is made. These two dynamic countervailing force requirements from the same hand sometimes causes the surgeon to apply too much handle pressure resulting in the 5 mm delivery tube puncturing the tissue causing excess bleeding and other trauma.
The distal end of the dart, the helical coil, and the shape metal fasteners are all pointed shaped and often twenty or more fasteners are used in a single case so that there are many sharply pointed fasteners that are implanted in the groin area. These fasteners can touch or penetrate nerves and cause severe pain that is more or less permanent unless they are removed in subsequent surgical procedures.
What is needed then is a hernia mesh fastener or anchor that is simple to deploy, does not have an implanted sharp distal point, and preferably is absorbed by the body after a period of time when the tissue in-growth to the mesh obviates the need for a fastener or anchor.
What is further needed is a simple inexpensive hernia mesh anchor deployment device that does not require simultaneous dynamic countervailing force to be applied by the same hand of the surgeon.